Energy Transfer Microparameters Research Articles

Fluorescence quenching mechanism for water-dispersible Nd3+:KYF4 nanoparticles synthesized by microwave-hydrothermal technique

We synthesize water-dispersible Nd3+:KYF4 nanoparticles with narrow size distribution by microwave-hydrothermal crystallization of freshly precipitated gels using the Emuksol-268 poloxamer as a surfactant. We detect the Nd3+ fluorescence in the material in the near-infrared spectral range, which is, however, partially quenched. We detect two types of optical sites and study the one with the higher energy of optical transitions. We obtain its kinetics of impurity quenching, which is attributed to Förster static quenching on –OH acceptors in the case of the low Nd3+ concentration of 0.1 at%. In the case of higher Nd3+ concentration of 1 at% we observe similar Förster-like kinetics with a higher decrement. Taking into account that the microparameter of energy migration CDDNd−Nd is significantly higher than the microparameter of energy transfer CDANd−OH we conclude that the Förster-like stage for the higher dopant concentrations is determined by hopping energy migration over the Nd3+ donors to –OH acceptors, and can therefore be described as the fluctuation kinetics. We estimate the values of the energy transfer microparameters which suggest that the level of impurity quenching for the Nd3+ doped fluoride nanoparticles is significantly lower than that of the previously reported phosphate nanoparticles with the same dopant. The fundamental reason is that the spontaneous emission lifetime τR is approximately six times longer in the case of fluoride nanoparticles. The results of energy transfer probing reveal that the –OH acceptors are distributed in the volume of the material (presumably in the mesopores of the nanoparticles) rather than on its surface, which is confirmed by lower fluorescence quenching in the Nd3+:KYF4 synthesized in D2O.

2.9μm emission properties and energy transfer mechanism in Dy3+/Tm3+-codoped tellurite glass

Abstract Dy 3+ and Dy 3+ /Tm 3+ -codoped tellurite–zinc glasses have been synthesized and studied by absorption and emission spectra. The Judd–Ofelt intensity parameters, energy transfer microparameters and efficiency have been determined and discussed. Intense 2.9 μm emission in Dy 3+ /Tm 3+ -codoped zinc–tellurite glasses was achieved under 800 nm laser diode excitation that confirms effective energy transfer from Tm 3+ to Dy 3+ ions. Possible energy transfer mechanism has been discussed based on the near- and mid-infrared emission spectra and the energy transfer microparameters. These results indicate that Dy 3+ /Tm 3+ -codoped tellurite–zinc glasses can be a potential medium for mid-infrared laser.

Enhanced 2.7 μm mid-infrared emission and energy transfer mechanism in Er3+/Nd3+ codoped tellurite glass

Nd3+ was introduced into Er3+ doped tellurite glass with composition of TeO2Nb2O5ZnONa2O to improve the 2.7μm band fluorescence upon the excitation of 800nm LD. The DSC curve and Raman spectrum were measured to characterize the thermal stability and vibration nature of glass host. The absorption spectra, visible, near- and mid-infrared fluorescence emission spectra were measured to evaluate the effects of Nd3+ introduction on the spectroscopic properties especially the 2.7μm band fluorescence of Er3+. It is shown that the prepared tellurite glass exhibits a large glass transition temperature and no obvious crystallization peak is observed in the measured temperature range of 200–550°C. Moreover, the introduction of Nd3+ significantly improves the 2.7μm band fluorescence intensity through joint energy transfer processes between the relevant excited levels of Er3+ and Nd3+, and the energy transfer mechanisms are further investigated in detail by calculating energy transfer micro-parameters and efficiency. The excellent thermal stability and strong 2.7μm fluorescence emission aroused by adopting codoping scheme indicate that the prepared Er3+/Nd3+ codoped tellurite glass is a potential glass medium applied for the 2.7μm mid-infrared band lasers.

Analysis of Energy Transfer and Concentration Quenching in Sm3+-Activated Borate GdB3O6 Phosphors by Means of Fluorescence Dynamics

This article reports on the optical properties of Sm3+-activated GdB3O6 phosphors based on the measurement of their photoluminescence spectra and luminescence decay curves. Energy transfer from Gd3+ to Sm3+ and the concentration quenching of the Sm3+ ion emission are investigated. From the photoluminescence spectra and decay curves, the energy transfer from Gd3+ to Sm3+ is confirmed. The concentration quenching of the Sm3+ ion emission can be ascribed to resonant cross-relaxation. The interaction between the Sm3+ ions is derived of the electric dipole–dipole type through fitting the data with the Inokuti-Hirayama model. The critical distances and energy transfer microparameter for the transfer processes are given. The decay curves of Sm3+4G5/2 level exhibiting a buildup and decay process also confirm the energy transfer from Gd3+ to Sm3+ and between Sm3+ ions.

Analysis on energy transfer process of Ho3+ doped fluoroaluminate glass sensitized by Yb3+ for mid-infrared 2.85 μm emission

This work reports the mid-infrared emission properties around 2.85μm in a Yb3+/Ho3+ codoped fluoroaluminate glass. This fluoroaluminate glass shows a good thermal stability and high transmittance around 3µm. The mid-infrared emission characteristics and energy transfer mechanism upon the excitation of the conventional 980nm laser diode have been investigated. The prepared glass possesses higher spontaneous transition probability (31.77s−1) along with the larger calculated emission cross section (1.91×10−20cm2) corresponding to the laser transition of Ho3+:5I6→5I7. Besides, the upconversion, 1.2μm and 2μm fluorescence spectra were measured to understand mid-infrared emission behavior together with decay curves of Ho3+:5I6 level. Moreover, energy transfer microparameters between Yb3+ and Ho3+ were calculated and discussed based on Dexter׳s model. Hence, the advantageous spectroscopic characteristics of Yb3+/Ho3+ codoped fluoroaluminate glass as well as the good thermal property indicate that this kind of glass is an attractive host for developing mid-infrared solid state laser.

Enhanced 2–5 μm emission in Ho3+/Yb3+ codoped halide modified transparent tellurite glasses

Ho3+/Yb3+ codoped TeO2–WO3–ZnO–ZnX2(X=F, Cl) glasses were prepared by melt-quenching method. The absorption spectra, transmittance spectra, X-ray diffraction (XRD) curves, Raman spectra and mid-infrared fluorescence spectra were measured, along with the Judd–Ofelt intensity parameters, stimulated emission and absorption cross-sections were calculated to evaluate the effects of halide amount of the spectroscopic properties. It is shown that the introduction of an appropriate amount of halide can further improve the mid-infrared fluorescence intensity through an enhanced phonon-assisted energy transfer between Ho3+/Yb3+ ions and the energy transfer mechanisms are investigated quantitatively in detail by calculating energy transfer microparameters and phonon contribution ratios. The results indicate that this kind of glasses is a promising material for mid-infrared optical fiber.

Multicolor upconversion emission and energy transfer mechanism in Er3+/Tm3+/Yb3+ codoped tellurite glasses

A novel Er3+, Tm3+ and Yb3+ codoped tellurite glasses with composition of TeO2–Bi2O3–ZnO–Na2O was prepared by conventional melt-quenching technique to realize the multicolor upconversion (UC) emissions. The absorption spectrum, UC emission spectrum, Raman spectrum, X-ray diffraction (XRD) and differential scanning calorimeter (DSC) curves were measured to characterize the prepared glass samples. Under the excitation of 980nm laser diode (LD), bright multicolor luminescence composed of red, green and/or blue UC emissions corresponding to the transitions 4F9/2→4I15/2, 2H11/2(4S3/2)→4I15/2 of Er3+ and 1G4→3H6 of Tm3+ were observed in the Er3+/Yb3+, Tm3+/Yb3+ and Er3+/Tm3+/Yb3+ codoped glass samples, which were mainly attributed to the successive energy transfers from Yb3+ to Er3+ and Tm3+, respectively. The energy transfer mechanisms from the Yb3+:2F5/2 level to Er3+:4I11/2 and Tm3+:3H5 levels were further investigated by quantitatively calculating the energy transfer micro-parameters and phonon contribution ratios. Meanwhile, the difference (ΔT=Tx−Tg) between the glass crystallization onset temperature (Tx) and the transition temperature (Tg) which increase slightly with rare-earth (RE) doped concentration, was larger than 140°C for all glass samples. Furthermore, the amorphous nature of glass structure was demonstrated by the measured XRD curves. The excellent thermal stability and multicolor luminescent characteristic indicate that the present investigated Er3+/Tm3+/Yb3+ codoped tellurite glasses could be used in the fields of solid state multicolor displays and other luminescent devices.

Enhanced 1.8 μm emission in Yb3+/Tm3+ co-doped tellurite glass: Effects of Yb3+↔Tm3+ energy transfer and back transfer

The ~1.8μm emission characteristics of Tm3+ by a direct excitation and through an energy transfer process upon sensitization with Yb3+ ions in tellurite glass are reported. The spectroscopic properties of Tm3+ ions have been evaluated by applying Judd–Ofelt theory on the measured absorption spectrum. The obtained intensity parameters, Ω2=7.155×10−20cm2, Ω4=3.325×10−20cm2, Ω6=1.278×10−20cm2 are used to estimate the radiative properties of Tm3+ ions in the present glass host. A ~10 fold enhancement in the Tm3+ 1.8μm emission observed with 16 fold reduced emission of Yb3+ ions (1008nm) in co-doped sample on Yb3+ ions excitation illustrates the efficient energy transfer from Yb3+: 2F5/2→Tm3+: 3H5. The energy transfer process assisted by host phonon energy has been discussed by using relevant theoretical models and estimated the energy transfer micro-parameters. Effect of energy back transfer Tm3+→Yb3+ on NIR and upconversion emissions have been discussed. An efficient ~1.8μm with comparatively higher emission cross-section 1.115×10−20cm2 on account of reduced upconversion emissions has been achieved in the present tellurite glass.

Impact of the ion–ion energy transfer on quantum computing schemes in rare-earth doped solids

We analyze the Ce3+–Pr3+:Y2SiO5 emission spectra obtained under selective excitation of the two Ce3+ sites in Y2SiO5 and we show clear evidence of direct energy transfer from Ce3+ to Pr3+. Energy transfer microparameters were calculated from the experimental spectral overlap between the Ce3+ emission and the Pr3+ and Eu3+ absorptions from which, the transfer mechanisms Ce3+→Pr3+ are concluded to be more efficient than the transfer mechanisms Ce3+→Eu3+. The energy transfer processes demonstrated here are potentially detrimental for an efficient qubit readout, using Ce3+ as readout ion, as they lead to a quenching of the Ce3+ luminescence and can give rise to the unwanted change of Pr3+ and Eu3+ qubit states. The quantum computing readout scheme is based on permanent electric dipole interactions scaling as R−3, where R is the distance between the Ce3+ and the qubit ion. The non-radiative energy transfer processes also depend on the ion–ion distances, however as R−6. A discussion about the microscopic dopant distributions leading to an efficient single-ion readout quantum computing scheme is here presented. The likely existence of energy transfer paths between the qubits or, as in this case, between the readout ion and the qubit ions, has not been taken into account so far by the rare-earth based quantum computing approaches. The results of this study suggest the need to consider them in order to design realistic and efficient quantum computing schemes for rare-earth doped solids.

Sensitizing effect of Ho3+ on the Er3+: 2.7 μm-emission in fluoride glass

The fluorescence properties of 2.7μm emission and energy transfer mechanism of Ho3+/Er3+ co-doped fluoride glass (ZBYA) have been investigated in the present paper. Ho3+ strengthens the Er3+: 2.7μm emission in the ZBYA glasses due to the energy transfer from Er3+ to Ho3+, while the 1.5μm emission decreases dramatically. The optimized concentration ratio of Er3+ to Ho3+ is found to be 1:1 in our glass system. The absorption and emission spectra are tested and the sample possesses large emission cross section (16.5×10−21cm2) around 2.7μm along with larger radiative transition probability (25.11S−1) on the basis of Judd–Ofelt and Fuchtbauer–Ladenburg theories. Additionally, the energy transfer microparameters are calculated using Förster–Dexter theory and the result shows the energy transfer coefficient of Er3+:4I13/2→Ho3+:5I7 is 24 times larger than that of Er3+:4I11/2→Ho3+:5I6. Our results show that Er3+: 2.7μm emission can be sensitized by Ho3+ efficiently, and this Er3+/Ho3+-codoped fluoride glasses might have potential application in mid-infrared lasers.

Er3+/Tm3+ codoped tellurite glass for blue upconversion—Structure, thermal stability and spectroscopic properties

The Er3+/Tm3+ codoped WO3 modified tellurite glasses with molar composition of (75−x)TeO2–20ZnO–5Na2O–xWO3–0.2wt%Er2O3–0.8wt%Tm2O3 (x=0,4,8,12mol%) were prepared to realize the blue upconversion emission. The absorption spectra, visible upconversion spectra and 1.53µm band fluorescence spectra of glass samples were measured, together with the quantitative calculations of relevant spectroscopic parameters of Tm3+ and energy transfer micro-parameters between Er3+ and Tm3+ ions, to evaluate the effects of WO3 oxide on the spectroscopic properties of Er3+–Tm3+ ions. It was found that the introduction of WO3 oxide can further improve the blue upconversion emission of Tm3+ through an enhanced phonon-assisted energy transfer process. Meanwhile, with the increase of WO3 amount, the thermal stability of glass hosts, characterized by the difference between the glass crystallization onset temperature and the transition temperature which obtained from the measured differential scanning calorimeter (DSC) curves, increased and no obvious crystallization peak was detected when the WO3 amount increased to 12mol%. Furthermore, the glass structure was briefly analyzed with the obtained Judd–Ofelt intensity parameters, the measured Raman spectra and X-ray diffraction (XRD) curves. The present results demonstrate the feasibility of realizing strong blue upconversion emission by introducing WO3 oxide with high phonon energy into the Er3+/Tm3+ codoped tellurite glass and also indicate its potential application as a glass host applied for the blue upconversion lasers.

Fluorescence characteristics and energy transfer of ytterbium-sensitized erbium-doped fluorophosphate glass for amplifier applications

Yb3+/Er3+ codoped fluorophosphate glass has been investigated for developing broadband waveguide amplifier application. Spectroscopic properties and energy transfer microparameters of prepared glasses have been discussed. The spectral components of 1.55μm emission are analyzed and an equivalent four-level system is proposed to estimate the stark splitting for the 4I15/2 and 4I13/2 levels in Er3+ doped fluorophosphate glass. The results indicate that highly doped Yb3+ ions could transfer energy to Er ions efficiently in fluorophosphate glass and Er3+/Yb3+ doped fluorophosphate glass is preferable for broadband Er3+-doped waveguide amplifier application.

Enhancement of the 1.53 μm fluorescence and energy transfer in Er3+/Yb3+/Ce3+ tri-doped WO3 modified tellurite-based glass

For the first time, the WO3 oxide with relatively high phonon energy was introduced into the Er3+/Yb3+/Ce3+ tri-doped tellurite-based glasses with composition of TeO2Bi2O3TiO2 to improve the 1.53μm band fluorescence emission. The X-ray diffraction (XRD) curves, Raman spectra, absorption spectra and 1.53μm band fluorescence spectra were measured, along with the Judd–Ofelt intensity parameters, stimulated emission and absorption cross-sections, and radiative quantum efficiencies were calculated to evaluate the effects of WO3 amount on the glass structure and spectroscopic properties especially the 1.53μm band fluorescence. It is shown that the introduction of an appropriate amount of WO3 oxide can further improve the 1.53μm band fluorescence intensity through an enhanced phonon-assisted energy transfer between Er3+/Ce3+ ions and the energy transfer mechanisms between Er3+/Yb3+ (Er3+/Ce3+) ions are investigated quantitatively in detail by calculating energy transfer microparameters and phonon contribution ratios. The results indicate that the prepared Er3+/Yb3+/Ce3+ tri-doped tellurite glass with an appropriate amount of WO3 oxide is a potential gain medium applied for the 1.53μm band broad and high-gain EDFA.

Spectroscopic properties and concentration effects on luminescence behavior of Nd3+ doped Zinc–Boro–Bismuthate glasses

A detail investigation on laser spectroscopic properties as a function of Nd3+ ions concentration in a new heavy metal oxide based Zinc–Boro–Bismuthate glasses is reported. The Judd–Ofelt analysis indicated an enhancement in Nd–O bond covalency as well as the local asymmetry of active ions on increase in dopant concentration from 0.1 to 1.5 mol%. Based on the Judd–Ofelt intensity parameters, several radiative properties such as transition probability, radiative lifetime, branching ratio and stimulated emission cross-section of Nd3+ ions have been derived. The luminescence intensity has showed a strong increase up to 0.5 mol% Nd2O3, which then attains maximum at 1 mol% and falls down for further increase in dopant concentration. The luminescence quenching behavior at higher dopant concentration has been attributed to the hopping migration assisted energy transfer mechanism leading to the cross-relaxation among active ions. The energy transfer micro-parameters for cross-relaxation (CDA) and donor energy migration (CDD) have been derived from the luminescence decay analysis as well as spectral overlap function respectively. The high stimulated emission cross-section and smaller cross-relaxation micro-parameters along with high quantum yield from the present glasses suggests their potential for compact infrared lasers and waveguide applications.

Spectroscopic properties of Er3+-doped fluorotellurite glasses

In this work we report the spectroscopic properties of Er3+-doped fluorotellurite glasses in the 46.6TeO2–18.2ZnO–35.2ZnF2 system for different ErF3 concentrations between 0.5 and 3wt%. Absorption and emission spectra and lifetimes have been measured in the visible and near infrared regions. Judd–Ofelt analysis has been performed to estimate the radiative transition probabilities. The high content of ZnF2 in this glass decreases the covalency degree in rare-earth site and results in a lower value of Ω2 if compared with zinc tellurite glasses. The infrared emissions at 1532nm are broader by nearly 30nm in these glasses if compared to silica glass. This broad emission together with the high values of the stimulated emission cross-section and lifetime of level 4I13/2 make these glasses attractive for broadband amplifiers. The decays from level 4I13/2 are single exponentials for all concentrations which indicates a fast energy diffusion between Er3+ ions. Similar values for the critical radius and energy transfer microparameter are obtained for the different concentrations, which supports the dipole–dipole transfer hypothesis.

Fluorescence properties and energy transfer study of Er3+/Nd3+ doped fluorophosphate glass pumped at 800 and 980 nm for mid-infrared laser applications

The fluorescence properties of 2.7 μm emission as well as near infrared emissions in Er3+/Nd3+ doped fluorophosphate glasses are investigated under 800 and 980 nm excitation. The fluorescence dynamics and energy transfer processes between Er and Nd ions in different pumping schemes are reported. Three Judd-Ofelt intensity parameters, energy transfer microparameters, and efficiency have been determined using the Judd-Ofelt and Förster-Dexter theories. The calculated energy transfer efficiency of the Er3+:4I13/2 level to the Nd3+:4I15/2 level is as high as 83.91%. The results indicate that Nd3+ may be an efficient sensitizer for Er3+ to obtain mid-infrared emission and the more suitable pumping scheme of 2.7 μm laser applications for Er3+/Nd3+ doped fluorophosphate glass is 980 nm excitation.

2.7 μm fluorescence radiative dynamics and energy transfer between Er 3+ and Tm 3+ ions in fluoride glass under 800 nm and 980 nm excitation

A detailed study of the fluorescence radiative dynamics and energy transfer processes between Er and Tm ions in the Er 3+/Tm 3+ doped fluoride glass is reported. The fluorescence properties of 2.7 μm emission, other infrared and visible emissions are investigated under different selective laser excitations. Three Judd–Ofelt intensity parameters, energy transfer microparameters and efficiency have been determined and discussed. It is found that present Er 3+/Tm 3+ doped fluoride glass possesses large calculated emission cross section (8.98×10 –21 cm 2) around 2.7 μm. The more suitable pumping scheme for laser applications at 2.7 μm laser is 980 nm excitation for Er 3+/Tm 3+ doped fluoride glass.

Spectroscopy of thulium and holmium heavily doped tellurite glasses

In this study, we report spectroscopic properties of Tm 3+ and Ho 3+ codoped tellurite glasses over a wide dopant concentration range in order to assess their potential laser performance under 790 nm diode laser excitation. The impact of Tm 3+ and Ho 3+ concentrations is investigated to identify specific candidates for fiber laser operation. The emission cross section is calculated and discussed, as well as the gain coefficient of this type of glasses. Energy transfer microparameters and critical ion distances are determined for 3H 4, 3F 4 (Tm 3+), and 5I 7 (Ho 3+) emission levels in the framework of diffusion-limited regime and dipole–dipole interaction. We also report thermal properties of tested glasses.

Energy transfer between Yb3+ and Er3+ ions in an Er,Yb:YAl3(BO3)4 crystal

The electron-excitation energy transfer between Er3+ and Yb3+ ions in Er,Yb:YAl3(BO3)4 crystals has been investigated. Crystals with different concentrations of active ions have been grown, and their luminescence decay kinetics in the spectral range near 1 μm have been experimentally measured. The energy-transfer microparameters have been calculated. It is shown that, to correctly describe the energy transfer in Er,Yb:YAl3(BO3)4 crystals, one must take into account the interactions of higher orders than dipole-dipole interactions.

Fluctuation kinetics of the hopping fluorescence quenching in disordered solid solutions: A theoretical model and experimental evidence

Fluctuation kinetics of the hopping fluorescence quenching in disordered solid solutions is investigated for the first time. Measurements were made in the chelated complexes of rare-earth ions [Y 1− x Tb x (pyca) 3(H 2O) 2] nH 2O used as chromophore. The Tb 3+ ions and the OH --ions of unbounded water molecules appear as fluorescent donors and randomly distributed acceptors, respectively, with the dipole–dipole interaction between them. The measured fluctuation kinetics is the kinetics of the Förster type but with larger decay amplitude. It begins almost immediately after the initial static stage of quenching, and lasts for the entire interval of measurements leaving no room at all for the well-known exponential kinetics with constant rate. Proposed theoretical explanation of the phenomenon is based on the solution of the closed many-particle integral equation for the observable kinetics of hopping fluorescence quenching. The methods for determination of the energy transfer microparameters by the measured fluorescence quenching kinetics are discussed.